Automatic gain control and wireless communication device

ABSTRACT

A wireless communication apparatus includes an antenna receiving a radio signal, a variable gain amplifier amplifying the received signal using a variable gain, an analog-to-digital converter converting the amplified signal into a digital signal, a gain setting unit periodically updating the gain of the variable gain amplifier in accordance with an output from the analog-to-digital converter, and an operating mode selection unit selecting one of a plurality of operating modes characterized by different gain updating periods in accordance with the output from the analog-to-digital converter, the selected operating mode being set in the gain setting unit. With this construction, the precision in conversion by the analog-to-digital converter is maintained at a proper level when an environment for signal reception varies.

TECHNICAL FIELD

The present invention relates to an automatic gain controllercontrolling a gain of a variable gain amplifier provided at an input ofan analog-to-digital converter, and also to a wireless communicationapparatus using the same.

BACKGROUND ART

FIG. 9 shows a wireless communication apparatus to which an automaticgain controller (AGC) according to the related art is applied. In thewireless communication apparatus, a signal received by an antenna 2 isamplified by an amplified 3 and a variable gain amplifier 4. AnI-component and a Q-component of the amplified signal are isolated by amixer 5. The isolated signals are then subject to analog-to-digitalconversion by analog-to-digital converters 6 i and 6 q, respectively andare decoded by a processing unit 7. An automatic gain controller 8calculates a difference between an output value of the analog-to-digitalconverter 6 i and a reference value and also calculates a differencebetween an output value of the analog-to-digital converter 6 q and thereference value so as to produce an error signal. The automatic gaincontroller 8 compares the error signal with a threshold value and so asto update the gain of the variable gain amplifier 4 at predeterminedintervals in accordance with a result of comparison. With thisconstruction, signals at a level adapted to the dynamic range of theanalog-to-digital converters 6 i and 6 q are input to theanalog-to-digital converters 6 i and 6 q so that the precision inconversion by the analog-to-digital converters 6 i and 6 q is maintainedat a proper level.

For example, published Japanese translation of PCT internationalpublication for patent application No. 10-506764 discloses automaticgain control in which the gain is controlled as a result of performingcomparison between the error signal and the threshold value.

In the related art, however, the gain is updated only after apredetermined period of time elapses even when the environment forreception changes as a result of, for example, a rapid variation in thelevel of received power. For this reason, a signal not adapted for thedynamic range of the analog-to-digital converter may be input to theanalog-to-digital converter when there is a rapid change in the level ofreceived power, resulting in decrease in the precision in conversion bythe analog-to-digital converter.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an automatic gaincontroller and a wireless base station in which a precision inconversion by an analog-to-digital converter is maintained at a properlevel even when an environment for reception is changed.

The present invention provides an automatic gain controller forcontrolling a gain of a variable gain amplifier provided at an input ofan analog-to-digital converter, comprising:

a gain setting unit periodically updating the gain of the variable gainamplifier in accordance with an output from the analog-to-digitalconverter; and

a mode selection unit selecting one of a plurality of operating modescharacterized by different gain updating periods in accordance withvariation in the output from the analog-to-digital converter, theselected operating mode being set in said gain setting unit.

According to this aspect of the invention, the gain of the variable gainamplifier is controlled in one of a plurality of operating modescharacterized by difference gain updating periods in accordance withvariation in the level of received power. Therefore, the gain of thevariable amplifier is controlled depending on variation in anenvironment for communication so that the precision in conversion by theanalog-to-digital converter is maintained at a proper level.

The present invention also provides a wireless communication apparatuscomprising:

an antenna receiving a radio signal;

a variable gain amplifier amplifying the received signal using avariable gain;

an analog-to-digital converter converting the amplified signal into adigital signal;

a gain setting unit periodically updating the gain of the variable gainamplifier in accordance with an output from a analog-to-digitalconverter; and

an operating mode selection unit selecting one of a plurality ofoperating modes characterized by difference gain updating periods inaccordance with variation in the output from said analog-to-digitalconverter, the selected operating mode being set in said gain settingunit.

According to this aspect of the invention, it is possible to control thegain of the variable gain amplifier in a wireless communicationapparatus to which the automatic gain control is applied, depending onvariation in an environment for communication. Therefore, the precisionin conversion by the analog-to-digital converter in the apparatus ismaintained at a proper level.

The present invention provides a wireless communication apparatuscomprising:

an antenna receiving a radio signal; an isolator isolating anI-component and a Q-component orthogonal to each other from the receivedsignal;

an I-component variable gain amplifier and a Q-component variable gainamplifier amplifying the isolated I-component and Q-component,respectively using a variable gain;

an I-component analog-to-digital converter and a Q-componentanalog-to-digital converter converting the amplified I-component andQ-component, respectively, into respective digital signals;

a gain setting unit periodically updating a gain common to saidI-component variable gain amplifier and said Q-component variable gainamplifier, in accordance with outputs from said I-componentanalog-to-digital converter and said Q-component analog-to-digitalconverter; and

an operating mode selection unit selecting one of a plurality ofoperating modes characterized by different gain updating periods inaccordance with variation in the outputs from said I-componentanalog-to-digital converter and said Q-component analog-to-digitalconverter, the selected operating mode being set in said gain settingunit.

According to this aspect of the invention, the gain of the I-componentvariable gain amplifier and the gain of the Q-component variable gainamplifier are centrally controlled in a wireless communication apparatusoperated on quadrature modulation. Therefore, the construction of theapparatus is simplified.

The present invention provides a wireless communication apparatuscomprising:

an antenna receiving a radio signal;

an isolator isolating an I-component and a Q-component orthogonal toeach other from the received signal;

an I-component variable gain amplifier and a Q-component variable gainamplifier amplifying the isolated I-component and Q-component using avariable gain;

an I-component analog-to-digital converter and a Q-componentanalog-to-digital converter converting the amplified I-component andQ-component into respective digital signals;

an I-component gain setting unit periodically updating a gain of saidI-component variable gain amplifier in accordance with an output fromsaid I—-component analog-to-digital converter;

an I-component operating mode selection unit selecting one of aplurality of operating modes characterized by different gain updatingperiods in accordance with variation in the output from said I-componentanalog-to-digital converter, the selected operating mode being set insaid I-component gain setting unit;

a Q-component gain setting unit periodically updating a gain of saidQ-component variable gain amplifier in accordance with an output fromsaid Q-component analog-to-digital converter; and

a Q-component operating mode selection unit selecting one of a pluralityof operating modes characterized by different gain updating periods inaccordance with variation in the output from said Q-componentanalog-to-digital converter, the selected operating mode being set insaid Q-component gain setting unit.

According to this aspect of the invention, the operating mode isselected for the I-component and the Q-component individually so thatthe gain of the variable gain amplifier 23 i and the gain of thevariable gain amplifier 23 q are controlled independently.

The present invention provides a wireless communication apparatuscomprising:

a first antenna and a second antenna receiving a radio signal:

a first variable gain amplifier and a second variable gain amplifieramplifying the signal received via said first antenna and secondantenna, respectively;

a first analog-to-digital converter and a second analog-to-digitalconverter respectively converting the amplified signals into respectivedigital signals;

a gain setting unit periodically updating a gain common to said firstvariable gain amplifier and second variable gain amplifier in accordancewith an output from said first analog-to-digital converter and an outputfrom said second analog-to-digital converter; and

an operating mode selection unit selecting one of a plurality ofoperating modes characterized by different gain updating periods inaccordance with variation in the outputs from said firstanalog-to-digital converter and said second analog-to-digital converter,the selected operating mode being set in said gain setting unit.

According to this aspect of the invention, signals from the first branchand the second branch are synthesized in a wireless communicationapparatus provided with diversity branches so that the gain setting unitcentrally controls the gain of the first variable gain amplifier and thegain of the second variable gain amplifier. Therefore, the constructionof the apparatus is simplified.

The wireless communication apparatus may further comprise a processingunit calculating a received power from the output value of theanalog-to-digital converter using the gain set in the gain setting unit.

According to this aspect of the invention, a digital outputcorresponding to an analog signal amplified by the variable gainamplifier is corrected to have a digital signal corresponding to ananalog signal before amplification so that an accurate received powermeasurement is made.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an electrical construction of awireless communication apparatus according to a first embodiment of thepresent invention.

FIG. 2 shows an operating mode of a gain setting unit 18.

FIG. 3 is a flowchart showing a flow of an automatic gain controlprocess.

FIG. 4 is a flowchart showing a frame check process of FIG. 3 in detail.

FIG. 5 is a flowchart showing a slot check process of FIG. 3 in detail.

FIG. 6 is a flowchart showing a gain control level setting process ofFIG. 3 in detail.

FIG. 7 is a block diagram showing an electrical construction of awireless communication apparatus according to a second embodiment of thepresent invention.

FIG. 8 is a block diagram showing an electrical construction of awireless communication apparatus according to a third embodiment of thepresent invention.

FIG. 9 shows a wireless communication apparatus according to the relatedart.

BEST MODE FOR CARRYING OUT THE INVENTION

The various embodiments of the invention will be described hereinafterwith reference to the attached drawings.

First Embodiment

FIG. 1 is a block diagram showing an electrical construction of awireless communication apparatus according to a first embodiment of thepresent invention. The wireless communication apparatus 10 comprises anantenna 11 a, a mixer 12, variable gain amplifiers (VGA) 13 i and 13 q,analog-to-digital converters 14 i and 14 q, a processing unit 15, and anautomatic gain controller (AGC) 19.

The antenna 11 receives a radio signal from a wireless terminal such asa portable terminal. The wireless terminal is configured to generate aradio signal by mixing an I component and a Q component by quadraturemodulation. The mixer 12 detects the signal from the antenna 11 so as toretrieve the I component and the Q component by a process of isolation.The variable gain amplifiers 13 i and 13 q respectively amplify the Icomponent and the Q component isolated by the mixer 12. Theanalog-to-digital converters 14 i and 14 q convert the analog signalsreceived from the variable gain amplifiers 13 i and 13 q, respectively,into digital signals. The processing unit 15 performs various processesincluding re-synthesis of the component signals and spectrumdespreading. The processing unit 15 also calculates the level ofreceived power from output values of the analog-to-digital converters 14i and 14 q, and from the level of gain control.

The automatic gain controller 19 is provided with an operation unit(I²+Q²) 16, a mode selection unit 17 and a gain setting unit 18, so asto control a common gain of the variable amplifiers 13 i and 13 q. Theoperation unit 16 calculates Σ(I²+Q²), based on the output values of theanalog-to-digital converters 14 i and 14 q. The mode selection unit 17selects a normal mode or a high-speed mode, based on the result ofcalculation, the normal mode and the high-speed mode being characterizedby different periods of update. The gain setting unit 18 updates thecommon gain of the variable gain amplifiers 13 i and 13 q in theoperating mode selected by the mode selection unit 17.

The processing unit 15 calculates the level of received power from theoutput values of the analog-to-digital converters 14 i and 14 q, and thelevel of gain control set by the gain setting unit 18. The processingunit 15 controls the power to be transmitted from the wirelesscommunication apparatus in accordance with the calculated level.Alternatively, the processing unit 15 informs a remote end with whichthe wireless communication apparatus is communicating of the level ofreceived power so that the remote end controls the level of transmissionaccordingly.

With this construction, the I component and the Q component are subjectto integrated control using the operation unit 16. The gain of thevariable amplifiers 13 i and 13 q is subject to integrated control bythe gain setting unit 18. Accordingly, the construction of the apparatusis simplified. Since the operation unit 16 performs a calculationΣ(I²+Q²), the I component and the Q component are equally weighted.Therefore, appropriate performance in control is guaranteed under anyenvironment for communication.

A description will now be given of the operation of the wirelesscommunication apparatus with reference to FIGS. 2–6.

FIG. 2 shows an operating mode of the gain setting unit 18. A frame isdefined as having a duration of 10 ms and a segment of a frame producedby division-by-15 is defined as one slot. A normal mode is defined as anoperating mode with a gain updating period of T1, which is relativelylong. A high-speed mode is defined as an operating mode with a gainupdating period of T2 (<T1), which is relative short. For example, asshown in FIG. 2, the period T1 may be equal to the duration of oneframe, i.e. 10 ms. The period T2 may be equal to the duration of 5slots, i.e. 10/3 ms. While the normal mode is being set, the gainsetting unit updates the gain at the period of T1. When the high-speedmode is set, the gain setting unit updates the gain at the period of T2.

FIG. 3 is a flowchart showing a flow of AGC process. In step a1, theprocess is started. In step a2, I²+Q² is calculated by the operationunit 16.

In step a3, I²+Q² is added to one-slot sum of signal power. In step a4,a determination is made as to whether the number of data items examinedreached the number of data items (for example, 5120) accommodated in oneslot. When it is determined that the number of data items does not reachthe total number for one slot, steps a2–a4 are repeated until the numberof data items reaches the total number. When the number of data itemsreaches the total number, the one-slot sum of signal power is divided bythe number of data items in one slot. Thus, through steps a3–a5, anaverage value of (I²+Q²) in one slot is calculated.

In step a6, a request is issued, the request being related either to aslot check process for determining whether a high-speed mode isnecessary, and to a frame check process for determining whether thenormal mode is necessary. When step a6 is completed, steps a7 and a8 areperformed. Control is then returned to step a2 whereupon theslot-averaging process is repeated. In step a7, the slot check processfor the high-speed mode is performed in accordance with the request. Instep a8, the frame check process is performed in accordance with therequest. Steps a7 and 8 are described later in detail with reference toFIGS. 4 and 5.

In step a9, the level of gain control is set. A detailed description ofstep a9 will be given later with reference to FIG. 6. In step a10, thelevel of gain control is output from the gain setting unit 18 to thevariable gain amplifiers 13 i and 13 q. In step all, the whole processis terminated.

FIG. 4 is a flowchart showing the frame check process of FIG. 3 indetail. In step b1, the frame check process is started. In step b2, adetermination is made as to whether there is a request for the framecheck process. When it is determined that the request is not provided,the determination step b2 is repeated until a positive determination isyielded. When there is a request for the frame check process, control isturned to step b3 where one-slot average value calculated in the processof FIG. 3 is added to one-frame sum of signal power.

In step b4, a determination is made as to whether the number of slotsreaches 15. When the number of slots reaches 15, control is turned tostep b5 where the one-frame sum of signal power is divided by 15 so asto obtain a frame average value. Thus, through steps b3–b5, theone-frame average value is calculated.

In step b6, a determination is made as to whether the one-frame averagevalue is lower than a lower margin Ls of a range of average values thatcalls for the normal mode or higher than the upper margin Us that callsfor the normal mode. If a negative answer is yielded in step b4 or instep b6, control is turned to step b7 where “0”, indicating a non-normalmode, is substituted in a normal operation flag NOR_FLAG. If anaffirmative answer is yielded in step b6, “1”, indicating the normalmode, is substituted in the normal operation flag NOR_FLAG.

Thus, in the frame check process of FIG. 4, steps b2–b8 are repeated sothat the normal operation flag NOR_FLAG is updated. Particularly, instep b6, variation in the received power is evaluated by examining theone-frame average value. The normal operation flag NOR_FLAG is set tothe normal mode or the non-normal mode depending on the result ofevaluation.

The upper margin Us and the lower margin Ls of a range of one-frameaverage value that calls for the normal mode are predetermined. Theupper margin Us is selected to be higher than the lower margin Ls.

FIG. 5 is a flowchart showing the slot check process of FIG. 3 indetail. In step c1, the slot check process is started. In step c2, adetermination is made as to whether there is a request for the slotcheck process. When it is determined that the request is not provided,the determination step c2 is repeated until a positive determination isyielded. When there is a request for the slot check process, control isturned to step c3 where a determination is made as to whether there isabsence of history indicating that high-speed mode was used in thepreceding slot. If the high-speed mode was used, i.e. if a negativeanswer is yielded in step c3, the determination steps c2 and c3 arerepeated.

If it is determined that the history indicates that the high-speed modewas not used in the preceding slot, i.e. if a positive answer is yieldedin step c3, control is turned to step c4 where a determination is madeas to whether the one-slot average value, determined in accordance withFIG. 3, is lower than a lower margin Lh that calls for the high-speedmode or higher than a higher margin Uh that calls for the high-speedmode. If an affirmative answer is yielded in step c4, control is turnedto step c5 where a determination is made as to whether an affirmativeanswer is yielded for a total of n consecutive slots, where n is aninteger greater than 1. If an affirmative answer is yielded in step c5,“1”, indicating the high-speed mode, is substituted in a high-speedoperation flag HI_FLAG in a subsequent step c6. If a negative answer isyielded in step c4 or in step c5, control is turned to step c7 where“0”, indicating a non-high-speed mode, is substituted in the high-speedoperation flag HI_FLAG in step c7.

Thus, in the slot check process of FIG. 5, steps c2–c7 are repeated sothat the high-speed operation flag is updated. Particularly, in steps c4and c5, variation in the received power is evaluated by examining theone-slot average value. The high-speed operation flag HI_FLAG is set tothe high-speed mode or the non-hish-speed mode depending on the resultof evaluation.

The upper margin Uh and the lower margin Lh of a range of one-slotaverage value that calls for the high-speed mode are predetermined. Theupper margin Uh is selected to be higher than the upper margin Us andthe lower margin Lh is selected to be lower than the lower margin Ls.

FIG. 6 is a flowchart showing in detail the process of setting the levelof gain control shown in FIG. 3. In step d1, the process of setting thelevel of gain control is started. In step d2, a determination is made asto whether the normal operation flag NOR_FLAG=0 and the high-speedoperation flag HI_FLAG=0. That is, a determination is made as to whetherboth the non-normal mode and the non-high-speed mode are called for.When it is determined that the non-normal mode and the non-high-speedmode are both called for, the determination step d2 is repeated until itis determined that either the normal mode or the high-speed mode iscalled for.

If a negative answer is yielded in step d2, i.e. if it is determinedthat the normal mode or the high-speed mode is called for, control isturned to step d3 where a determination is made as to whether thehigh-speed operation flag HI_FLAG=1, i.e. whether the high-speed mode iscalled for. If it is determined that the high-speed mode is called for,control is turned to step d4 where the level of gain control is set to±XdB, where X indicates a real number greater than 1, whereupon controlis returned to step d2. If it is determined in step d3 that thehigh-speed mode is not called for, it is determined that the normal modeis called for. In step d5, the level of gain control is set to ±1 dB sothat control is returned to step d2.

According to the process of setting the level of gain control shown inFIG. 6, the level of gain control is updated in accordance withvariation in the received power, by repeating steps d2–d5 after settingthe level of gain control in step d4 or in step d5. Steps a3 of FIG. 3through d3 are performed in the mode selection unit 17. Step d4 and thesubsequent steps are performed in the gain setting unit 18.

As described, according to the first embodiment, the gain of thevariable gain amplifier is updated in one of the two operating modescharacterized by different updating periods, in accordance withvariation in the received power. Thus, it is possible to control thegain of the variable gain amplifier in accordance with a change in theenvironment for communication. That is, even when the environment forcommunication changes, the analog-to-digital converters continue toreceive signals adapted for the dynamic range thereof so that theprecision in conversion by the analog-to-digital converters ismaintained at a proper level.

One particular application is wireless base stations of a code divisionmultiple access (CDMA) system which are normally characterized by onlyslight variation in the received power. In these base stations, amoderate gain control is favorable. Therefore, the normal mode accordingto the invention may suitably be employed for control. In rare cases,where there is an abrupt change in the power, the high-speed mode may beemployed for control so that the urgent need for keeping track of thevariation is properly met. Accordingly, it is possible to effect controladapted for the environment for communication.

In the foregoing description of the first embodiment, it is assumed thatquadrature modulation producing the I component and the Q component, 90°phase-displaced from each other, is employed. The present invention mayfind applications in other type of modulation including a simplemodulation. The level of gain control in the normal mode may be otherthan ±1 dB. Although it is assumed that the calculation Σ(I²+Q²) isperformed, the operation unit 16 may perform other types ofcalculations. For example, ΣI² and ΣQ² are calculated separately so thatthe common gain of the variable gain amplifiers 13 i and 13 q is setbased on these results of calculation.

Second Embodiment

FIG. 7 is a block diagram showing an electrical construction of awireless communication apparatus according to a second embodiment of thepresent invention. The wireless communication apparatus 20, which is avariation of the wireless communication apparatus of the firstembodiment, comprises an antenna 21, an amplifier 21 a, a mixer 22,variable gain amplifiers (VGA) 23 i and 23 q, analog-to-digitalconverters 24 i and 24 q, a processing unit 25, and an automatic gaincontroller (AGC) 29. The antenna 21, the amplifier 21 a, the mixer 22,the variable gain amplifiers (VGA) 23 i and 23 q, the analog-to-digitalconverters 24 i and 24 q, and the processing unit 25 are the same as thecorresponding components of FIG. 1 so that the description thereof isomitted.

The automatic gain controller 29 is provided with an operation unit (I²)26 i, an operation unit (Q²) 26 q, mode selection units 27 i and 27 q,and gain setting units 28 i and 28 q so as to control the gain of thevariable amplifiers 23 i and 23 q individually. The operation units 26 iand 26 q calculate square sums Σ(I²) and Σ(Q²) respectively, based onsignals from the analog-to-digital converters 24 i and 24 q,respectively. The mode selection units 27 i and 27 q each selects one ofa plurality of operating modes characterized by difference updatingperiods, based on the results of operation in the operation units 26 iand 26 q, respectively. The gain setting units 28 i and 28 q update thegain of the variable gain amplifiers 23 i and 23 q, respectively, in theoperating mode selected by the mode selection units 27 i and 27 q,respectively.

With this construction, the operating mode for the I-component and thatfor the Q-component are set individually so that the gain of thevariable gain amplifier 23 i and the gain of the variable gain amplifier23 q are controlled independently.

The operation for selecting the operating mode of the gain setting units28 i and 28 q is the same as the corresponding operation according tothe first embodiment shown in FIGS. 2–6, so that the description thereofis omitted. Accordingly, the advantage available in the first embodimentis also available in the second embodiment. That is, the gain of thevariable gain amplifier is updated in one of a plurality of operatingmodes characterized by different updating periods, in accordance withvariation in the received power. Accordingly, the gain of the variablegain amplifier is adaptively controlled depending on the environment forcommunication.

Third Embodiment

FIG. 8 is a block diagram showing an electrical construction of awireless communication apparatus according to a third embodiment of thepresent invention. The wireless communication apparatus 30, a variationof the wireless communication apparatus of the first embodiment,comprises antennas 31 and 41, the amplifiers 31 a and 41 a, mixers 32and 42, variable gain amplifiers (VGA) 33 i, 33 q, 43 i, 43 q,analog-to-digital converters 34 i, 34 q, 44 i, 44 q, a processing unit35, and an automatic gain controller (AGC) 49.

The antennas 31, the amplifier 31 a, the mixer 32, the variable gainamplifiers (VGA) 33 i and 33 q, and the analog-to-digital converters 34i and 34 q constitute a first branch for diversity reception. Thesecomponents are the same as the corresponding components of FIG. 1 sothat the description thereof is omitted. The antenna 41, the amplifier41 a, the mixer 42, the variable gain amplifiers (VGA) 43 i and 43 q,and the analog-to-digital converters 44 i and 44 q constitute a secondbranch for diversity reception. These components are the same as thecorresponding components of FIG. 1 so that the description thereof isomitted. The processing unit 35 is also the same as the correspondingunit of FIG. 1.

The automatic gain controller 49 is provided with an operation unit(I²+Q²) 36, an operation unit (I²+Q²) 46, a mode selection unit 37, again setting unit 38, and correction units 40 and 50, so as to controlthe gain of the variable gain amplifiers 33 i, 33 q, 43 i and 43 q. Theoperation unit 36 calculates Σ(I²+Q²), based on signals from theanalog-to-digital converters 34 i and 34 q. The operation unit 46calculates Σ(I²+Q²), based on signals from the analog-to-digitalconverters 44 i and 44 q.

A power comparison unit 39 compares power of the two branches. The modeselection unit 37 selects one of a plurality of operating modescharacterized by different updating periods, based on a result ofcomparison by the power comparison unit 39. The gain setting unit 38periodically updates the common gain of the variable gain amplifiers 33i, 33 q, 43 i and 43 q in the operating mode selected by the modeselection unit 37. The correction units 40 and 50 each stores the levelof gain control effective for an initial state in which an externalradio signal is not received in the corresponding one of the branches.The level of gain control effected upon reception of the radio signal iscorrected by the corresponding one of the correction units 40 and 50 andset in the variable gain amplifier in the corresponding one of thebranches. More specifically, each of the correction units makes acorrection to cancel difference in the level of gain control requireddue to irregularity in products constituting each of the branches sothat the total gain of the branches match.

With this construction, the I component and the Q component aresynthesized by the operation units 36 and 46, whereupon the signals fromthe first branch and the second branch are synthesized by the powercomparison unit 39, so that the gain of the variable gain amplifiers 33i, 33 q, 43 i and 43 q are centrally controlled by the gain setting unit38. Accordingly, the construction of the apparatus is simplified. Sincethe operation units 36 and 46 perform a calculation Σ(I²+Q²), the Icomponent and the Q component are equally weighted. Therefore, properperformance in control is guaranteed under any environment forcommunication.

The operation of the gain setting unit 38 for selecting the operatingmode is the same as the corresponding operation of the first embodimentshown in FIGS. 2–6, so that the description thereof is omitted.Accordingly, the advantage available in the first embodiment is alsoavailable in the third embodiment. That is, the common gain of thevariable gain amplifiers is updated in one of a plurality of operatingmodes characterized by different updating periods, in accordance withvariation in the received power. Accordingly, the gain of the variablegain amplifiers is adaptively controlled depending on the environmentfor communication and the precision in conversion by theanalog-to-digital converters is maintained at a proper level.

In the third embodiment, the I component and the Q component arecentrally controlled. Alternatively, the components may be controlledindividually as in the second embodiment. In the third embodiment, thefirst branch and the second branch are described as being centrallycontrolled. Alternatively, the branches may be controlled individually.

INDUSTRIAL APPLICABILITY

The automatic gain controller and the wireless communication apparatusaccording to the present invention are suitably used in wireless basestations and wireless terminals of the CDMA system.

1. An automatic gain controller configured to control a gain of avariable gain amplifier provided at an input of an analog-to-digitalconverter, comprising: a gain setting unit configured to periodicallyupdate the gain of the variable gain amplifier in accordance with anoutput from the analog-to-digital converter; and a mode selection unitconfigured to select for each frame a single operating mode of aplurality of operating modes characterized by different gain updatingperiods based on either a one-frame average value or a one-slot averagevalue of the output from the analog-to-digital converter, the selectedoperating mode being set in said gain setting unit, wherein one frameincludes a plurality of slots.
 2. A wireless communication apparatuscomprising: an antenna configured to receive a radio signal; a variablegain amplifier configured to amplify the received signal using avariable gain; an analog-to-digital converter configured to convert theamplified signal into a digital signal; a gain setting unit configuredto periodically update the gain of the variable gain amplifier inaccordance with an output from an analog-to-digital converter; and anoperating mode selection unit configured to select for each frame asingle operating mode of a plurality of operating modes characterized bydifferent gain updating periods based on either a one-frame averagevalue or a one-slot average value of the output from saidanalog-to-digital converter, the selected operating mode being set insaid gain setting unit, wherein one frame includes a plurality of slots.3. A wireless communication apparatus comprising: an antenna configuredto receive a radio signal; an isolator configured to isolate anI-component and a Q-component orthogonal to each other from the receivedsignal; an I-component variable gain amplifier and a Q-componentvariable gain amplifier configured to amplify the isolated I-componentand Q-component, respectively, using a variable gain; an I-componentanalog-to-digital converter and a Q-component analog-to-digitalconverter configured to convert the amplified I-component andQ-component, respectively, into respective digital signals; a gainsetting unit configured to periodically update a gain common to saidI-component variable gain amplifier and said Q-component variable gainamplifier, in accordance with outputs from said I-componentanalog-to-digital converter and said Q-component analog-to-digitalconverter; and an operating mode selection unit configured to select foreach frame a single operating mode of a plurality of operating modescharacterized by different gain updating periods based on either aone-frame average value or a one-slot average value of the outputs fromsaid I-component analog-to-digital converter and said Q-componentanalog-to-digital converter, the selected operating mode being set insaid gain setting unit, wherein one frame includes a plurality of slots.4. A wireless communication apparatus comprising: an antenna configuredto receive a radio signal; an isolator configured to isolate anI-component and a Q-component orthogonal to each other from the receivedsignal; an I-component variable gain amplifier and a Q-componentvariable gain amplifier configured to amplify the isolated I-componentand Q-component using a variable gain; an I-component analog-to-digitalconverter and a Q-component analog-to-digital converter configured toconvert the amplified I-component and Q-component into respectivedigital signals; an I-component gain setting unit configured toperiodically update a gain of said I-component variable gain amplifierin accordance with an output from said I-component analog-to-digitalconverter; an I-component operating mode selection unit configured toselect for each frame a single operating mode of a plurality ofoperating modes characterized by different gain updating periods basedon either a one-frame average value or a one-slot average value of theoutput from said I-component analog-to-digital converter, the selectedoperating mode being set in said I-component gain setting unit; aQ-component gain setting unit configured to periodically update a gainof said Q-component variable gain amplifier in accordance with an outputfrom said Q-component analog-to-digital converter; and a Q-componentoperating mode selection unit configured to select for each frame asingle operating mode of a plurality of operating modes characterized bydifferent gain updating periods based on either a one-frame averagevalue or a one-slot average value of the output from said Q-componentanalog-to-digital converter, the selected operating mode being set insaid Q-component gain setting unit, wherein one frame includes aplurality of slots.
 5. A wireless communication apparatus comprising: afirst antenna and a second antenna configured to receive a radio signal:a first variable gain amplifier and a second variable gain amplifierconfigured to amplify the signal received via said first antenna andsecond antenna, respectively; a first analog-to-digital converter and asecond analog-to-digital converter respectively configured to convertthe amplified signals into respective digital signals; a gain settingunit configured to periodically update a gain common to said firstvariable gain amplifier and second variable gain amplifier in accordancewith an output from said first analog-to-digital converter and an outputfrom said second analog-to-digital converter; and an operating modeselection unit configured to select for each frame a single operatingmode of a plurality of operating modes characterized by different gainupdating periods based on either a one-frame average value or a one-slotaverage value of the outputs from said first analog-to-digital converterand said second analog-to-digital converter, the selected operating modebeing set in said gain setting unit, wherein one frame includes aplurality of slots.
 6. The wireless communication apparatus according toclaim 2, further comprising a processing unit configured to calculate areceived power from the output value of the analog-to-digital converterusing the gain set in the gain setting unit.
 7. The wirelesscommunication apparatus according to claim 3, further comprising aprocessing unit configured to calculate a received power from the outputvalue of the analog-to-digital converter using the gain set in the gainsetting unit.
 8. The wireless communication apparatus according to claim4, further comprising a processing unit configured to calculate areceived power from the output value of the analog-to-digital converterusing the gain set in the gain setting unit.
 9. The wirelesscommunication apparatus according to claim 5, further comprising aprocessing unit configured to calculate a received power from the outputvalue of the analog-to-digital converter using the gain set in the gainsetting unit.
 10. The automatic gain controller according to claim 1,wherein the operating mode selection unit is configured to selectbetween a high-speed mode and a normal mode, and the operating modeselection unit is configured to select the high-speed mode when theone-frame average value lies outside a first range and the one-slotaverage value lies outside a second range for each of a plurality ofconsecutive slots, the first range being a lesser included range of thesecond range.
 11. A wireless communication apparatus according to claim2, wherein the operating mode selection unit is configured to selectbetween a high-speed mode and a normal mode, and the operating modeselection unit is configured to select the high-speed mode when theone-frame average value lies outside a first range and the one-slotaverage value lies outside a second range for each of a plurality ofconsecutive slots, the first range being a lesser included range of thesecond range.
 12. The wireless communication apparatus according toclaim 3, wherein the operating mode selection unit is configured toselect between a high-speed mode and a normal mode, and the operatingmode selection unit is configured to select the high-speed mode when theone-frame average value lies outside a first range and the one-slotaverage value lies outside a second range for each of a plurality ofconsecutive slots, the first range being a lesser included range of thesecond range.
 13. The wireless communication apparatus according toclaim 4, wherein each of the operating mode selection units isconfigured to select between a high-speed mode and a normal mode, andeach of the operating mode selection units is configured to select thehigh-speed mode when the respective one-frame average value lies outsidea first range and the respective one-slot average value lies outside asecond range for each of a plurality of consecutive slots, the firstrange being a lesser included range of the second range.
 14. Thewireless communication apparatus according to claim 5, wherein theoperating mode selection unit is configured to select between ahigh-speed mode and a normal mode, and the operating mode selection unitis configured to select the high-speed mode when the one-frame averagevalue lies outside a first range and the one-slot average value liesoutside a second range for each of a plurality of consecutive slots, thefirst range being a lesser included range of the second range.
 15. Amethod of controlling a gain of a variable gain amplifier provided at aninput of an analog-to-digital converter, comprising: periodicallyupdating the gain of the variable gain amplifier in accordance with anoutput from the analog-to-digital converter; and selecting for eachframe a single operating mode of a plurality of operating modescharacterized by different gain updating periods based on either aone-frame average value or a one-slot average value of the output fromthe analog-to-digital converter, the selected operating mode being setin said gain setting unit, wherein one frame includes a plurality ofslots.
 16. The automatic gain controller according to claim 15, whereinthe step of selecting one of a plurality of operating modes includes:selecting between a high-speed mode and a normal mode; and selecting thehigh-speed mode when the one-frame average value lies outside a firstrange and the one-slot average value lies outside a second range foreach of a plurality of consecutive slots, the first range being a lesserincluded range of the second range.
 17. An automatic gain controllerconfigured to control a gain of a variable gain amplifier provided at aninput of an analog-to-digital converter, comprising: a gain setting unitconfigured to periodically update the gain of the variable gainamplifier in accordance with an output from the analog-to-digitalconverter; and means for selecting for each frame a single operatingmode of a plurality of operating modes characterized by different gainupdating periods based on either a one-frame average value and or aone-slot average value of the output from the analog-to-digitalconverter, the selected operating mode being set in said gain settingunit, wherein one frame includes a plurality of slots.
 18. The automaticgain controller according to claim 17, wherein the means for selectingone of a plurality of operating modes includes: means for selectingbetween a high-speed mode and a normal mode; and means for selecting thehigh-speed mode when the one-frame average value lies outside a firstrange and the one-slot average value lies outside a second range foreach of a plurality of consecutive slots, the first range being a lesserincluded range of the second range.